Solid-state imaging device, solid-state imaging apparatus and manufacturing method thereof

ABSTRACT

A solid-state imaging apparatus includes a plurality of unit pixels with associated microlenses arranged in a two-dimensional array. Each microlens includes a distributed index lens with a modulated effective refractive index distribution obtained by including a combination of a plurality of patterns having a concentric structure, the plurality of patterns being divided into line widths equal to or shorter than a wavelength of an incident light. At least one of the plurality of patterns includes a lower light-transmitting film having the concentric structure and a first line width and a first film thickness, and an upper light-transmitting film having the concentric structure configured on the lower light-transmitting film having a second line width and a second film thickness. The distributed index lens has a structure in which a refractive index material is dense at a center and becomes sparse gradually toward an outer side in the concentric structure.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of pending U.S. patent applicationSer. No. 11/423,776, filed Jun. 13, 2006, the disclosure of which isexpressly incorporated herein by reference in its entirety.

This application claims priority of Japanese Patent Application No.2005/178585, filed Jun. 17, 2005, the disclosure of which is expresslyincorporated by reference herein.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a solid-state imaging apparatus usedfor a digital camera and the like, and a manufacturing method thereof.

(2) Description of the Related Art

Along with the widespread use of an imaging device-related products (adigital camera, a camera-equipped mobile phone and the like), the marketof the solid-state imaging apparatus has been remarkably developed. Inthe current of such development, the needs have changed to a wide anglein addition to a high sensitivity and a high pixel density (hereafter,called as “high pixel”) of the solid-state imaging apparatus due to atendency to a thin camera module with a tendency to a thin digital stillcamera, a thin mobile phone and the like. A downsizing of a cameraoptical system indicates that a lens used for the camera module becomesto have a short focal length. More particularly, a light is incident ona solid-state imaging apparatus with a wide angle (in other words, awide angle measured from a vertical axis of an incidence plane of asolid-state imaging device composing a solid-state imaging apparatus).

In the present, in a charged-coupled device (CCD) and a metal oxidesemiconductor (MOS) Imaging device that are commonly used as solid-stateimaging apparatuses, a solid-state imaging device (called as “pixel”)which are semiconductor integrated circuits having a light-receivingunit are arranged in a two-dimensional array, in which a light signalfrom an object is converted into an electric signal.

The sensitivity of the solid-state imaging apparatus is defined based onan amount of output current of a light-collecting device to an amount ofincident light, so that leading the incident light surely into thelight-collecting device is an important factor for improving thesensitivity.

FIG. 5 is a diagram showing an example of a basic structure of aconventional solid-state imaging device. As shown in FIG. 5, a light 58(light indicated by dashed lines) which is incident vertically into amicrolens 60 is separated into colors using one of red (R), green (G),and blue (B) color filters 2, and then converted into an electric signalat a light-receiving device 6. Since relatively high light-collectingefficiency can be obtained conventionally, the microlens is used inalmost all solid-state imaging devices.

In the future development of a solid-state imaging device supporting awide angle incidence, it is necessary to lead an incident light at aspecific angle surely into the light-collecting device.

However, in the conventional microlens, the light-collecting efficiencydecreases depending on the incident angle of a signal light. Moreparticularly, in FIG. 5 the light 58 which is incident vertically intothe microlens 60 can be collected with high efficiency, while a light 59(light indicated by solid lines) which is incident obliquely into themicrolens 60 is collected with relatively lower efficiency. This isbecause that the light 59 which is incident obliquely is intercepted atan Al interconnection 3 in a solid-state imaging device, so that thelight 59 does not reach the light-receiving device 6.

As described above, the solid-state imaging apparatus is made up ofmultiple pixels that are arranged in a two-dimensional array. Therefore,in the case of incident light with a spread angle, the angle ofincidence differs between the pixels in the central area and the pixelsnear the edge (refer to FIG. 2). As the result, there is a problem thatthe light-collecting efficiency of the pixels near the edge decreasesthan that of the pixels in the central area.

FIG. 3 is an example of a cross-sectional diagram showing pixels nearthe edge. The incident angle of the incident light is relatively greaterat pixels near the edge. Therefore, the improvement of thelight-collecting efficiency is sought by displacing electric wiringparts to the inner direction which means by shrinking.

FIG. 4 is a diagram showing a dependency on an incident angle of thelight-collecting efficiency of the solid-state imaging device using amicrolens. It shows that the light-collecting efficiency of thesolid-state imaging device using a microlens is relatively high for theincident light of the incident angle of around 20°. However, thelight-collecting efficiency declines suddenly for the incident light ofthe incident angle of more than 20°. As the result, the amount of lightcollected at pixels near the edge is about 40 percent of that at thepixels in the central area, and the sensitivity of the whole pixels islimited by the sensitivity of the pixels near the edge at present. Thisvalue further declines with the decrease of the pixel size so that itsapplication to an optical system with a short focal length such as asmall-sized camera becomes very difficult. Furthermore, in amanufacturing method thereof, there is a problem that further circuitshrinking is not possible.

In view of aforesaid problem, it is necessary to design a microlenswhich is able to support the incident angle in order to prevent adecrease of the sensitivity of the solid-state imaging device associatedwith the increase of incident angle. However, although the current pixelsize of the solid-state imaging device is as extremely fine as 2.2 μm,finer size of pixel is needed in order to realize further high pixeldensity in the future. Thus, processing of microlens is executed on asub-micron basis, so that forming the microlens by the currently usedthermal reflow processing is not possible.

As described above, in order to realize the solid-state imaging deviceapplicable to an optical system (an optical system with a high incidentangle θ) with a short focal length for a thin camera, a new type oflight-collecting device, which can be formed by easy fine processing andalso the light-collecting device whose light-collecting efficiency isnot lowered even when an incident angle is high, comparing withmicrolens, needs to be developed.

In recent years, along with development of a planar process technologyrepresented by optical lithography and electron beam lithography, alight-collecting device (Subwavelength Lens: SWLL) having a periodicstructure of a sub-wavelength draws an attention. Here, a sub-wavelengtharea indicates an area with the same size as the wavelength of a lightconcerned or an area smaller than that. A certain research group of auniversity has substantiated that an aspherical Fresnel lens is changedto an SWLL having grid pattern, so that a light-collecting effect can beexpected (for example Non-patent reference 1). As a method, theconventional Fresnel lens (FIG. 1 (a)) is divided by an area 61 of λ/2n(λ: wavelength of incident light, n: refractive index of lens material),so as to obtain a linear approximation (FIG. 1 (b)) and a rectangularapproximation (FIG. 1 (c)) in each area, and thus the SWLL is formed. Inaddition, in the same way, it has been reported that a line width in astructure in a sub-wavelength area can be controlled, so that a blazedbinary optical diffraction device can be formed, and thus diffractionefficiency is improved (for example Patent Reference 1).

If the SWLL could be used as the light-collecting device for thesolid-state imaging device, the microlens could be formed using ageneral semiconductor process, and also the shape of microlens could becontrolled without limitation.

However, the divided period of the SWLL (for example the area 61 inFIG. 1) is strongly dependent on a wavelength of incident light.Therefore, the divided period becomes 0.1 to 0.3 μm in an opticalwavelength area. By the aforesaid method, the blazed binary opticaldiffraction device needs to be formed by further microstructure (0.01 to0.1 μm), and forming such microstructure is extremely difficult by thecurrently available process.

Non-patent Reference 1: Opt. Eng. 38 870-878, D. W. Prather, 1998 PatentReference 1: Japanese Laid-Open Patent 2004-20957

SUMMARY OF THE INVENTION

In view of the aforesaid problem, an object of the present invention isto provide a solid-state imaging apparatus and the like which is able tosupport an optical system whose incident angle is wide.

In the present invention, a distributed index lens which provides thesame effect has been invented by a discretization of the refractiveindex distribution in an area with about a half of width of thewavelength of the incident light in size. The structure of the lens ofthe present invention is on a boundary theoretically between an area ofa resonance in diffractive optics and an area of effective refractivemethod. At this time, the incident light is affected by both therefractive index of the material itself and the refractive index whichis averaged based on the structure. As a result, the distributed indexlens includes light-collecting characteristics of both a distributedindex lens and a film thickness distribution lens, so that thecollecting efficiency is higher than the conventional distributed indexlens.

In addition, the line width of the basic structure stays constant by asub-micron basis, so that the process conditions such as lithography andetching can be identical between pixels. As a result, the process can beperformed with ease and high accuracy.

In view of the aforesaid problem, a solid-state imaging device accordingto the present invention, a light-collecting device includes acombination of a plurality of zone areas with a concentric structure,the plurality of zone areas being divided into line width which areequal to or shorter than a wavelength of an incident light, at least oneof the plurality of zone areas includes: a lower light-transmitting filmwith the concentric structure and having a first line width and a firstfilm thickness; and an upper light-transmitting film with the concentricstructure, configured above the lower light-transmitting film, andhaving a second line width and a second film thickness. According tothis configuration, the manufacture of the light-collecting device (thedistributed index lens) following the conventional semiconductor planerprocess can be realized, so that the solid-state imaging device withhigh accuracy can be provided.

In addition, in a part of a vertical cross-section including a center ofthe light-collecting device, a light-transmitting film, which is formedby combining the upper light-transmitting film and the lowerlight-transmitting film, may form a convex portion, a light-transmittingfilm, which is formed by combining the upper light-transmitting film andthe lower light-transmitting film, may form a concave, alight-transmitting film, which is formed by combining the upperlight-transmitting film and the lower light-transmitting film, may forma step-like portion, and a light-transmitting film, which is formed bycombining the upper light-transmitting film and the lowerlight-transmitting film, may form a rectangle portion.

In addition, in the light-collecting device, a light incoming side has asparse structure, and an effective refractive index on the lightincoming side is lower than an effective refractive index on a lightoutgoing side. According to this configuration, a convex lens can beformed, so that the lens with high light-collecting efficiency can beformed.

In addition, in the light-collecting device, a light outgoing side has asparse structure, and an effective refractive index on the lightoutgoing side is lower than an effective refractive index on a lightincoming side. According to this configuration, the process formanufacture of the distributed index lens can be simplified, so that thecost required for the manufacture can be reduced.

In addition, in the light-collecting device, the respective line widthsare defined as approximately λ/2 μl, where λ denotes a wavelength of anincident light and n denotes a refractive index. According to this, thelens includes light collecting characteristics of both a distributedindex lens and a film thickness distribution lens, so that thelight-collecting efficiency is higher than the conventional distributedindex lens.

In addition, in the light-collecting device, each line width is an equalline width. According to this, the line width of the basic structurestays constant, so that the process for manufacture of the distributedindex lens can be performed with ease and high accuracy.

In addition, the second film thickness is greater than the first filmthickness. According to this, the reproducibility of the refractiveindex (low n area) can be improved. In other words, the amount of changein a high refractive index area becomes greater and the amount of changein a low refractive index area becomes smaller with the change of thestructure, so that the refractive index (low n area) can be controlledmore easily.

In addition, the second film thickness is smaller than the first filmthickness. According to this, the reproducibility of the refractiveindex (high n area) can be improved. In other words, the amount ofchange in a high refractive index area becomes smaller and the amount ofchange in a low refractive index area becomes greater with the change ofthe structure, so that the refractive index (high n area) can becontrolled more easily.

In addition, light-collecting device is formed by at least two kinds oflight-transmitting materials with different refractive indexes.According to this, the strength of the lens is increased and thecontamination is decreased, so that the reliability of the lens can beraised.

In addition, the light-collecting device is formed by the plurality oflight-transmitting materials whose refractive index difference is notmore than 0.5. According to this, the light-collecting efficiency at thetime of low incident angle (0 to 20°) can be raised.

In addition, the light-collecting device is formed by the plurality oflight-transmitting materials whose refractive index difference is 0.5and more. According to this, the light-collecting efficiency at the timeof high incident angle (20 to 40°) can be raised.

In addition, the light-collecting device includes one of TiO₂, ZrO₂,Nb₂O₅, Ta₂O₅, Si₃N₄ and Si₂N₃. These are the materials having highrefractive index and enable to make the film thickness of thelight-collecting device thin, so that the manufacture process can besimplified.

In addition, the light-collecting device includes one of SiO₂ doped withB or P, that is Boro-Phospho Silicated Glass, and Teraethoxy Silane.These are the materials generally used in the conventional semiconductorprocess and enable to form the light-collecting device with ease, sothat the manufacture cost can be reduced.

In addition, the light-collecting device includes one ofbenzocyclobutene, polymethymethacrylate, polyamide and polyimide. Theresign can be processed by a tool directly, so that a mass productioncan be raised.

In addition, in the light-collecting device, a structure of alight-transmitting film in a vertical cross-section including a centerof the light-collecting device, which is formed by combining the upperlight-transmitting film and the lower light-transmitting film, isdifferent depending on a wavelength of an incident light. According tothis, the lens structure of each pixel can be optimized based on thewavelength of the incident light, so that, the difference of thelight-collecting efficiency between colors can be eliminated.

In addition, in the light-collecting device, the structure of thelight-transmitting film is different depending on focal length settingfor a collected light. According to this, the focus distance of theincident light is variable, so that the lens design suitable for eachpixel structure is possible.

In addition, in the light-collecting device, the structure of thelight-transmitting film is different depending on an incident angle ofthe incident light. According to this, the light-collecting devicecorresponding to the incident angle of the incident light can be formed,so that the solid-state imaging device which is strong to a wide angleincidence can be realized.

In addition, the light-collecting device includes a light-transmittingfilm, which is formed by combining the upper light-transmitting film andthe lower light-transmitting film, as an in-layer lens. According tothis, the strength of the lens can be increased.

In addition, a light-transmitting film, which is formed by combining theupper light-transmitting film and the lower light-transmitting film,forms a taper structure in the cross-section structure. According tothis, a change of the refractive index on the cross-section iscontinuous, and the reflection component on the surface becomes smaller,so that the light-collecting efficiency can be improved.

In addition, in one of the zone areas, a position of the upperlight-transmitting film and a position of the lower light-transmittingfilm are shifted by a predetermined misalignment margin. According tothis, regarding the upper light-transmitting film and the lowerlight-transmitting film configuring the light-collecting device, thepositioning of each film is done considering a misalignment generatedwhen these films are positioned, so that an adverse effect caused by amisalignment between the position of the upper light-transmitting filmand the position of the lower light-transmitting film can be reduced, asa result the process can be simplified.

In addition, the solid-state imaging apparatus including unit pixelsthat are arranged in a two-dimensional array, each unit pixel includinga light-collecting device, the light-collecting device includes acombination of a plurality of zone areas with a concentric structure,the plurality of zone areas being divided into line width which areequal to or shorter than a wavelength of an incident light, and at leastone of the plurality of zone areas includes: a lower light-transmittingfilm with the concentric structure and having a first line width and afirst film thickness; and an upper light-transmitting film with theconcentric structure, configured above the lower light-transmitting, andhaving a second line width and a second film thickness. According tothis, the solid-state imaging apparatus including a light-collectingdevice with high light-collecting efficiency can be provided.

In addition, a center of the concentric structure of thelight-collecting device is shifted from a center of the unit pixel.According to this, the sensitivity of the solid-state imaging device canbe improved.

In addition, the light-collecting device is formed on a whole area ofthe corresponded unit pixel. According to this, the aperture ratiobecomes higher, so that the sensitivity of the solid-state imagingdevice can be improved.

In addition, a total thickness of the first film thickness and thesecond film thickness in the light-collecting device in the unit pixelwhich locates in a center of the apparatus is greater than a totalthickness of the first film thickness and the second film thickness inthe light-collecting device in the unit pixel which locates near an edgeof the apparatus. According to this, color shadings between pixels andthe difference of the amount of the incident light can be reduced.

In addition, the solid-state imaging apparatus includes alight-receiving device, in the unit pixels located in the center of theapparatus, a central axis of each of the light-receiving devices isplaced to match a central axis of each of the light-collecting devices,and in the unit pixels located near the edge of the apparatus, a centralaxis of each of the light-receiving devices and a central axis of eachof the light-collecting devices are placed toward the center of thesolid-state imaging apparatus. According to this, the lens structure canbe simplified and also a high light-collecting efficiency can beexpected, so that the sensitivity of the solid-state imaging device canbe improved.

In addition, a method for manufacturing a solid-state imaging apparatusaccording to the present invention which includes unit pixels that arearranged in a two-dimensional array, each unit pixel including alight-collecting device which has a light-transmitting film with apredetermined film thickness and a light-receiving device, the methodincluding: forming a semiconductor device integrated circuit, in whichthe light-receiving device, an interconnection, a light-shielding layer,and a signal transmission unit are mounted on an Si substrate;depositing a light-transmitting film on the semiconductor integratedcircuit; processing the light-transmitting film so as to form aconcentric structure; forming a film made of Bottom Anti-reflectionCoating and a resist on the processed light-transmitting film; andforming a lower light-transmitting film with the concentric structurewith a first film thickness and an upper light-transmitting film withthe concentric structure with a second film thickness. According tothis, the conventional semiconductor process can be used, so that thecost required for the manufacture can be reduced.

The solid-state imaging device having aforesaid lens structure enablesto improve a resolution and the sensitivity, and moreover themanufacturing process can be simplified.

Further Information about Technical Background to this Application

The disclosure of Japanese Patent Application No. 2005-178585 filed onJun. 17, 2005 including specification, drawings and claims isincorporated herein by reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and features of the invention willbecome apparent from the following description thereof taken inconjunction with the accompanying drawings that illustrate a specificembodiment of the invention. In the Drawings:

FIG. 1 is a cross section diagram showing a structure of conventionalsub-wavelength lens;

FIG. 2 is a diagram showing a basic structure of a conventional pixelarray;

FIG. 3 is a diagram showing a basic structure of a conventionalsolid-state image device;

FIG. 4 is a diagram showing the light-collecting efficiency of thesolid-state image device using a conventional microlens;

FIG. 5 is a diagram showing an example of a basic structure of aconventional solid-state imaging device;

FIG. 6 is a diagram showing a basic structure of a solid-state imagingdevice of the first embodiment;

FIG. 7 is a diagram showing a three-dimensional structure of one pixelof the first embodiment;

FIG. 8 is a top view diagram of a distributed index lens of the firstembodiment;

FIG. 9 is a cross-sectional diagram of the distributed index lens of thefirst embodiment;

FIG. 10 is a diagram showing basic patterns of a film thickness betweena high refractive index material and a low refractive index material ineach zone area having two-stage concentric circle structure of the firstembodiment;

FIG. 11 is a diagram showing a refractive index distribution (equalpitch) of the lens of the first embodiment;

FIG. 12 is a diagram showing a refractive index distribution (unequalpitch) of the lens of the first embodiment;

FIG. 13 is a diagram showing a basic structure forming the distributedindex lens (unequal pitch) of the first embodiment;

FIG. 14 is a diagram showing a phase modulation of a light of the firstembodiment;

FIG. 15A to FIG. 15G are diagrams showing a manufacturing process of thedistributed index lens of the first embodiment;

FIG. 16 is a diagram showing a pixel array in a solid-state imagingdevice of a second embodiment;

FIG. 17 A to FIG. 17 C are diagrams showing a basic structure of onepixel which is dependent on an incident angle of the second embodiment;

FIG. 18 A to FIG. 18 C are diagram a showing refractive indexdistributions of three kinds of lenses of the second embodiment;

FIG. 19 is a diagram showing a light transmission profile in a pixel ofthe second embodiment;

FIG. 20 is a diagram showing a light-collecting efficiency of thesolid-state imaging device of the second embodiment;

FIG. 21 is a diagram showing a basic structure of one pixel of a thirdembodiment;

FIG. 22 is a diagram showing a cross-sectional diagram of thedistributed index lens of a fourth embodiment;

FIG. 23 A to FIG. 23 D are diagrams showing a manufacturing process ofthe distributed index lens of the fourth embodiment;

FIG. 24 is a diagram showing a light-collecting efficiency of thesolid-state imaging device of the fourth embodiment;

FIG. 25 A and FIG. 25 B are diagrams showing a light transmissionprofile in a pixel of a fifth embodiment;

FIG. 26 is a diagram showing a light-collecting efficiency of thesolid-state imaging device of the fifth embodiment;

FIG. 27 is a diagram showing a pixel array in a solid-state imagingdevice of a sixth embodiment;

FIG. 28 is a diagram showing a cross-sectional diagram of thedistributed index lens of a seventh embodiment;

FIG. 29 is a diagram showing a countermeasure for a misalignment of aposition occurred during lithography of an eighth embodiment; and

FIG. 30 is a cross sectional diagram showing a solid-state imagingdevice of a ninth embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereafter, embodiments of the present invention will be describedreferring to diagrams. It should be noted that the present inventionwill be explained using the embodiments below and the attached diagramsjust as examples, and it is obvious that the present invention is notlimited to these examples.

First Embodiment

FIG. 6 is a diagram showing a basic structure of a solid-state imagingdevice according to the present embodiment. As shown in FIG. 6, thesolid-state imaging device (also called as pixel) 100 is 2.25 μm squarein size, and includes a distributed index lens 1, a color filter 2, anAl interconnections 3, a signal transmitting unit 4, a planarized layer5, a light-receiving device (Si photodiodes) 6, and an Si substrate 7(note that as shown in FIG. 6, from the Al interconnections 3 to the Sisubstrate 7 is also called as a semiconductor integrated circuit 8).

FIG. 7 is a diagram showing a three-dimensional structure of thesolid-state imaging device 100 shown in FIG. 6. FIG. 7 shows just simplythe distributed index lens 1 (for 0°), the Al interconnections 3 and thelight-receiving device 6. FIG. 7 also shows that the distributed indexlens 1 having a two-stage concentric structure (more specifically, atwo-stage concentric circle structure) is equipped as a component in thesolid-state imaging device 100.

FIG. 8 is a top view diagram of the distributed index lens 1 shown inFIG. 6. The concentric circle structure of the distributed index lens 1,which is composed of SiO₂ (n=2), is formed by two-stage concentriccircle structure with the film thicknesses 0.4 μm (t₁) and 0.8 μm (t₂)as shown in FIG. 6. It should be noted that the concentric circlestructure of an upper/a lower is defined as an upper light-transmittingfilm/a lower light transmitting film in the description. In FIG. 8, theparts of the film thickness 1.2 μm are shown with “fine dots” and theparts of film thickness 0.8 μm are shown with “coarse dots”. Note thatthe parts with the film thickness of 0 μm are shown “without pattern:white color”. The structure of the distributed index lens 1 of thepresent embodiment is formed by engraving SiO₂ so as to make aconcentric circle structure, and the medium surrounding the distributedindex lens 1 is air (n=1).

Here, the shape of the area where the distributed index lens 1 beingformed is rectangular in accordance with the aperture of each pixel. Ingeneral, in the case where the shape of the incident window area iscircle, gaps between lenses are generated. Therefore, light is leakedfrom the gaps, so that a light-collecting loss is increased. However,when the shape of the incident window is rectangular, it is possible tocollect incident light with the whole area of the pixel. Therefore,light does not leak, so that the light-collecting loss can be reduced.

FIG. 9 is an example of a detailed cross-sectional diagram of thedistributed index lens 1 of the present embodiment. The refractive indexof such general distributed index lens shows its highest index at theoptical center. As shown in FIG. 9, in the case of the presentembodiment, SiO₂ is densely collected around the optical center 14, andbecomes sparse towards the outer zone area. Here, in a case where thewidth of each zone area (hereafter called as “line width d”) 13 isalmost same as or less than a width of a wavelength of an incidentlight, an effective refractive index which a light senses is definedaccording to a volume ratio (the volume ratio is equal to “a thicknessratio” in the case of the concentric circle structure) between a highrefractive index material (for example, SiO₂) and a low refractive indexmaterial (for example, air). More specifically, when the high refractiveindex material is increased in the zone area, the effective refractiveindex is raised, while when the high refractive index material isdecreased in the zone area, the effective refractive index is lowered.

FIG. 10 is a diagram showing basic patterns of the film thicknessbetween the high refractive index material and the low refractive indexmaterial in each zone area having two-stage concentric circle structure.FIG. 10 (a) shows a structure of the most densely collected structure,and more specifically the effective refractive index of this structureis the highest, and the effective refractive index becomes lower towardsFIG. 10 (f). At this time, the upper film thickness t₁ 15 at lightincident side is 0.4 μm and the lower film thickness T₂ 16 at substrateside is 0.8 μm, and the film thickness ratio (upper/lower) is 0.5. Here,in the case where the aforesaid thickness ratio is changed, theeffective refractive index can be controlled. For example, when thethickness ratio is increased, the decrease of the volume of the highrefractive index material is relatively big due to the change of thebasic structures (from FIG. 10 (a) towards FIG. 10 (f)). Thus, thedecrease of the refractive index in the area with high effectiverefractive index becomes greater. On the contrary, when the thicknessratio is lowered, the decrease of the volume of the high refractiveindex material is relatively small. Thus, the decrease of the refractiveindex in the area with low effective refractive index becomes big.

In the present embodiment, the basic structures such as FIG. 10 (a) toFIG. 10 (f) are used as an example for easier description. However,other structures can be used. For example, a convex structure bycombining FIG. 10 (b) and FIG. 10 (c) can be used, and also a concavestructure by combining FIG. 10 (b) and FIG. 10 (d) can be used. At thistime, in the case where such structures are used in the area with abouthalf-width of the wavelength of the incident light, the samelight-collecting characteristic can be obtained.

The most distinguished characteristic of the present invention is thatthe combination of the basic structures can be changed, so that therefractive index distribution can be controlled without constraints. Inthe present invention, the change of the refractive index of thedistributed index lens 1 is represented by a solid line in FIG. 11. Therefractive index of the distributed index lens 1 is the highest at thecenter area of the circle, and the refractive index becomes lowertowards the edge. The parabolic arch indicates a refractive indexdistribution. The parabola indicated in FIG. 11 shows a refractive indexdistribution for collecting incident light with a wavelength λ (550 nm)in a focal length f (3.0 μm), and it is denoted by the followingequation:

$\begin{matrix}\begin{matrix}{{\Delta \; {n(x)}} = {\Delta \; {n_{\max}\left\lbrack {\frac{\left( {{Ax}^{2} + {{Bx}\; {Sin}\; \theta}} \right)}{2\pi} + C} \right\rbrack}}} & \left( {A,B,{C\text{:}\mspace{14mu} {constants}}} \right)\end{matrix} & (1)\end{matrix}$

Here, Δn_(max) indicates a difference of refractive indexes (this caseis 1.43) between an incoming side medium and a lens material.Furthermore, in the equation (1), the parameters can be set by theequations below, where the refractive index on the incoming side mediumis n₀, and the refractive index on the outgoing side medium is n₁:

A=−(k ₀ n ₁)/2f  (2)

B=−k ₀ n _(o)  (3)

k ₀=−2π/λ  (4)

Thus, a lens can be optimized according to the respective factors: adesired focal length, an incident angle of the incident light to beobjected, and (or) a wavelength. It should be noted that the termdefined by quadric of a distance x from the pixel center denotes acollecting-light component, and the term defined by product of x andtrigonometric function denotes a deflection component respectively inthe equation (1).

The parabolic defined by the equation (1) is continuous obviously, andshows an ideal refractive index distribution. However, according to theactual micro optic system (sub-micron area), forming a continuousdistribution is extremely difficult, and the process loads is so heavy.According to the present invention, a discretization by the area notmore than half-width of an incident light wavelength is used for therefractive index distribution of a lens. Thus, the same effect can beachieved successfully. For example, the discretization by an equalperiod basis (that is, line width d₀) is used for the refractive indexdistribution as shown in FIG. 11. Accordingly, the line width of thebasic structure can be constant, and the process condition (lithography,etching and the like) can be equalized between pixels. As a result, theprocess can be performed with ease and high accuracy.

As an alternative, the discretization by an unequal period basis (thatis, d₁>d₂>d₃>d₄>d₅) is used for the refractive index distribution asshown in FIG. 12. It should be noted that, in this case, each line widthis defined to equalize the refractive index. The structure of thedistributed index lens of this case is shown in FIG. 13, and therefractive index lens is structured by combining a high refractive indexmaterial and a low refractive index material in the areas havingdifferent line widths respectively. The advantage of this structure isthat the refractive index distribution can be divided so as to make therefractive index distribution equal, so that the reproducibility of therefractive index distribution is high and the light-collectingefficiency can be improved.

Note that FIG. 8 shows a lens structure using 0° of the incident lightangle, and an equal pitch as the dividing method, and then the center ofthe optics corresponds to the center of each pixel.

In the present embodiment, a phase modulation of the incident light isperformed depending on the refractive index, so as to control atransmission direction of the light. At this time, the phase modulationobtained by the equation (1) is a discontinuous phase modulation, whichare indicated by not only the first zone 18, but also the second zone19, the third zone 20 and the like, obtained by dividing the equation(1) by 2π, as shown in FIG. 14. However, the zone is divided every onephase, and therefore an effective phase modulation equals to acontinuous phase modulation 17 (denoted by a solid line curve).

The second characteristic of the present invention is that a lightcollecting generated by the refractive index distribution can bestrengthened by a film thickness distribution. In general, in thediffraction optics, a structure greater than a wavelength issystematized by Fourier optics, and a structure smaller than awavelength is systematized by the effective refractive index method. Alight is regarded as a line in the former case, while a light isregarded as a wave in an electromagnetic field in the latter case. Aresonance area is an area placed between the aforesaid two theoreticalregions, and the behavior of a light is allowed in either a line or anelectromagnetic wave.

Here, in the lens structure of the present invention, the width of thedivided each zone area is set as around λ/2n, which is on the boundarybetween the resonance area and the effective refractive index method. Inthis state, the incident light senses both a refractive index of thematerial itself, and a refractive index (effective refractive index)which is equalized according to the structure. As a result, the lens hasthe light-collecting characteristics of both the distributed index lensand the film thickness distribution lens, so that the light-collectingeffectiveness becomes higher than a conventional distributed index lens.

FIG. 15 A to FIG. 15 G are diagrams showing a manufacturing process ofthe distributed index lens of the present invention. The distributedindex lens has a two-stage concentric circle structure, andphoto-lithography and etching are performed two times respectively inthe process. Firstly, a light-receiving device, an inter-connection, alight-shielding layer, a signal transmitting unit and a color filter areplaced on an Si substrate so as to form a semiconductor circuit 8 (notindicated in FIG. 15) using a general semiconductor manufacturingprocess. One pixel is 2.25 μm square in size, and the light-receivingdevice is 1.5 μm square in size. After that, an SiO₂ film 23 is formed,and a resist 22 is coated thereon using a CVD (Chemical VaporDeposition) device. Then, a patterning is performed by a light exposure25 (refer to FIG. 15 A). The thickness of the SiO₂ film is 1.2 μm andthe resist is 0.5 μm respectively.

After developing, a fine structure is formed on the pixel surface byetching 26 (FIG. 15 B and FIG. 15 C). After removing the resist, BARK(Bottom Anti-reflection Coating) is embedded so as to planarize thesurface (FIG. 15 D). After applying the resist, a patterning isperformed by the light exposure 25 again (FIG. 15 E). After the etching(FIG. 15 F), the resist and the BARK are removed so as to form the lensof the present invention (FIG. 15 G).

In the present embodiment, forming a lens having two-stage concentriccircle structure is shown. In addition, a lens having plural stages(more than three stages) can be formed by a process combiningphoto-lithography and etching. The more the number of stages isincreased, the more the limit of the resolution is increased, so thatthe light-collecting efficiency is improved.

Hereafter, the aforesaid process is used in forming of the distributedindex lens.

Second Embodiment

FIG. 16 is a diagram showing a pixel array in a solid-state imagingdevice using a video graphics array (VGA) (310,000 pixels) of the secondembodiment. A signal light 28 is collected into an optical lens 29, andirradiated on the solid-state imaging device 30 having a lens. In thesolid-state imaging device in which a semiconductor integrated circuitincluding a light-receiving device, interconnections and the like anddistributed index lens 32 (or 34) are arranged in a two-dimensionalarray, the incident angle of light is different for pixels in a centerpart and for pixels near the edge. While the incident light 31 enters atapproximately 0° into the pixels in the center part, the incident light33 enters at the incident angle of approximately 30° into the pixelsnear the edge. Accordingly, in the present embodiment, the distributedindex lenses corresponding to the incident light component with thestrongest light intensity that is incident into each pixel are formedfrom the center part towards the edge of the solid-state imaging device.Each distributed index lens optimizes the lens structure depending onthe position of the pixel on the solid-state imaging device so that thelight-collecting efficiency becomes the highest.

FIG. 17 A to FIG. 17 C are diagrams showing a basic structure of pixelswhich is dependent on an incident angle (pixel position). Thedistributed index lenses 38, 29 and 40 have refractive indexdistribution denoted by the equation (1) relative to the incident light.A light 35 incoming to an incident window at incident angle of 0° iscollected into a distributed index lens 38 for an incident light 0°, alight 36 incoming to an incident window at incident angle of α/2° iscollected into a distributed index lens 39 for an incident light a/2°, alight 37 incoming to an incident window at incident angle of α° iscollected into a distributed index lens 40 for an incident light a α°.Then, the light passes a color filter 2, and then converted into anelectric signal.

According to the distributed index lenses 38, 39 and 49 of the presentembodiment, the structure of the lens in each pixel can be optimizeddepending on a wavelength of the incident light, so that there is nodifference of the light-collecting efficiency depending on incidentangle, and the light-collecting efficiency can be high. In thedistributed index lens 38 for an incident light 0°, the center of theconcentric circle is located at a pixel center. When the incident angleis increased, the center of the concentric circle is shifted to theincident side of the light.

This is because that, as shown in the equation (1), the maximum value ofa quadratic curve for the refractive index distribution shifts toincident light side with the increase of incident angle θ (refer to FIG.18 A to FIG. 18 C). At this time, the concentric circle structure of thelens is asymmetrical to the pixel area (refer to FIG. 17 B and FIG. 17C).

In addition, it is obvious from the relation of the parameters A, B, andK₀, the phase modulation is different depending on the wavelength of thelight to be incident. This indicates that the lens has an optimum lensstructure depending on the light color incoming into each pixel. In thepresent embodiment, in the case where light of respective wavelengths of0.45 μm, 0.55 μm and 0.65 μm are incident on each pixel having a lensstructure of each color, it is known that each pixel has a highlight-collecting efficiency of around 80 percent.

FIG. 19 is a diagram showing a simulation result of a light transmissionprofile in a pixel for the incident light with the incident angle of45°. It can be seen in the diagram that the transmission direction ofthe incident light is refracted at the time of passing the lens, and theincident light focuses at the first interconnection (light-shieldinglayer), and then the light is transmitted to the light-receiving device.This indicates that the distributed index lens which is made inaccordance with the equation (1) enables to transmit the lightefficiently to the light-receiving device.

FIG. 20 is a diagram showing a dependency on an incident angle of thelight-collecting efficiency. The angle on the x-axis indicates an angleof the light incident to the solid-state imaging device, and 0° is theincident light to the pixels at the center part, while 300 or higherindicate the light incident to the pixels at the edge. Thelight-collecting efficiency of the solid-state imaging device using aconventional microlens declines sharply at around the pixels of theincident angle 20°, while the light-collecting efficiency of thedistributed index lens of the present invention maintains 60% even thepixels at the edge. Furthermore, in the area around the incident angle40°, the light-collecting efficiency is four times of that of themicrolens.

It is obvious from FIG. 20 that the distributed index lens of thepresent invention is superior in the angle dependency of the incidentlight comparing with the microlens. According to this, the decline ofthe light-collecting efficiency along with the increase of the incidentangle can be moderated. Therefore, it can be expected that thedistributed index lens of the present invention is applicable to a shortfocal length optic system such as a camera equipped in a mobile phone.

Third Embodiment

FIG. 21 is a diagram showing the distributed index lens of the presentembodiment composed of two kinds of the light-transmitting materialsother than air The distributed index lens does not include an air area,so that the dynamic range of the refractive index variation isdecreased. However, the surface of the lens can be planarized, so thatthe scattering loss can be decreased. In addition, it is possible todeposit other light-transmitting materials on the lens, so that thedistributed index lens of the present invention is applicable formultilayer film. Furthermore, the strength of the lens is reinforced, sothat higher durability of the distributed index lens can be implemented.In the present invention, the distributed index lens is used as one ofan in-layer lens, and it is obvious that the distributed index lens canbe used as a lens placed on the top. At this time, the distributed indexlens performs as a film to protect the lens from contaminations.

Fourth Embodiment

FIG. 22 is a diagram showing the distributed index lens with concavestructure of the forth embodiment. The first characteristic of thedistributed index lens of the fourth embodiment is that the structure ofthe light incident side is relatively wider, and the structure of thesubstrate side is relatively narrower. Such distributed index lens withconcave structure has more planarity on the lens surface, so that thescattering loss of the incident light on the surface is lowered, and thelight-collecting efficiency can be improved. The second characteristicof the distributed index lens of the fourth embodiment is that themanufacturing process can be simplified and an easier fine processingcan be implemented.

FIG. 23 A to FIG. 23 D are diagrams showing a manufacturing process ofthe distributed index lens of the present embodiment. The lens is formedby optical lithography and etching. Firstly, a light-receiving device,an interconnection, a light-shielding layer, a signal transmitting unit,a color filter and the like are placed on the Si substrate using anordinary semiconductor manufacturing process so as to form asemiconductor integrated circuit (not indicated in FIG. 23 A to FIG. 23D). One pixel is 2.25 μm square in size, and the light-receiving deviceis 1.5 μm square in size. After that, an SiO₂ film 23 as a lowrefractive material is formed, and a resist 22 is coated thereon using aCVD device. Then, a pattering is performed by an optical lithography(refer to FIG. 23 A). The thickness of the SiO₂ is 1.2 μm and the resistis 0.5 μm respectively. As described in the first embodiment using FIG.15, the patterning, the embedding of BARK, and the etching 26 areiterated in the manufacturing process of the semiconductor integratedcircuit, so as to form a two-stage concentric circle structure (FIG. 23B). After the resist and the BARK are removed (FIG. 23 C), an SiN42 isembedded thereon using the CVD (FIG. 23D). Lastly, the surface of thelens is planarized, so as to form the distributed index lens of SiO₂ onwhich SiN is embedded.

The manufacturing process shown in FIG. 23 enables to form a lens of ahigh refractive material such as SiN, TiO₂ and the like, on which a fineprocessing being difficult to be conducted generally, composed of thehigh refractive material with a silica system material and a resinmaterial as a basic component. In addition, the light-transmittingmaterials can be embedded on the upper part and the lower part of thelens at the same time, so that the number of manufacturing processes canbe decreased, and the cost required for the manufacture can be reduced.

FIG. 24 is a diagram showing a dependency on an incident angle of thelight-collecting efficiency. The light-collecting efficiency of thesolid-state imaging device using a conventional microlens declinessharply at around the incident angle 200 of pixel, while thelight-collecting efficiency of the distributed index lens of the presentinvention maintains 50% in the nearby pixels (in the area of theincident angle 40°).

Fifth Embodiment

FIG. 25 A and FIG. 25 B are diagrams showing a simulation result of alight transmission profile in a pixels of the distributed index lenscomposed of two kinds of materials (incident 0°). FIG. 25 A shows a caseof a lens with a small difference of the refractive index, and it can beseen in the diagram that the incident light focuses at the firstinterconnection (light-shielding layer), and then the light istransmitted to the light-receiving device. This indicates that thedistributed index lens enables to transmit the light efficiently to thelight-receiving device. FIG. 25 B shows a case of a lens with a highdifference of the refractive index, and it can be seen in the diagramthat the reflection light and the scattering light component becomesbigger, so that the amount of the light which reaches thelight-receiving device is decreased.

FIG. 26 is a diagram showing a dependency on an incident angle of thelight-collecting efficiency. As described above, a lens with a smalldifference of the refractive index has a higher light-collectingefficiency in the low angle incident area. However, the light-collectingefficiency of the lens with a bigger difference of the refractive indexcan be raised along with the increase of the incident angle. This isbecause that when the difference of the refractive index is bigger, anoptical path length (=refractive index of lens: n*lens film thickness:to) becomes longer, so that the deflection is improved. The same effectcan be obtained by changing the lens film thickness.

Sixth Embodiment

FIG. 27 is a diagram showing a pixel array in a solid-state imagingdevice using a video graphics array (VGA) (310,000 pixels) of the sixthembodiment. The signal light 28 is collected into the optical lens 29,and irradiated on the solid-state imaging device 30 having thedistributed index lenses (composed of BCB (Benzocyclobutene)/SiN) 46, 47and 48. The resin materials such as BCB enable to form a thick film andenable to provide an easier post process, so that the distributed indexlens with high light-collecting efficiency can be formed. In the pixelsat the center part with lower incident angle, the lens film thicknesst_(a) is thinner (0.6 μm). The lens film thickness is increased towardsthe edge along with the increase of the incident angle. In the pixel foran incident 40°, the film thickness t_(c) is 1.0 μm. The distributedindex lens is optimized according to the incident angle, so that thesensitivity of the whole pixels is improved, while the signal strengthof the pixels near the edge is decreased by about 20%.

Seventh Embodiment

FIG. 28 is a diagram showing the distributed index lens whose crosssection is a taper structure of the seventh embodiment. The crosssection of the light-transmitting film in each zone is a taper structurewhose line width is getting thicker towards the incident lightdirection. There is no sudden reflection change with this structure, sothat the scattering and reflection of the light on the surface of thelens can be reduced, and the incident light can be collected into thepixel efficiently. As a result, the light-collecting efficiency can beimproved. On the other hand, the cross section of the light transmittingfilm in each zone is a rectangular structure (refer to FIG. 9), therefractive index change sensed by the incident light is increased, sothat the light collecting and the deflection of the lens are improved.The determination on which structure is used depends on the purpose ofthe solid-state imaging device. It is preferable that in the case of thedevice for low angle incident light, the taper-lens with high efficiencyof light collecting is used, while in the case of the device for highangle incident light, the rectangular-lens with higher deflection isused respectively.

Eighth Embodiment

FIG. 29 is a diagram showing a countermeasure for a misalignment of aposition occurred during lithography.

In the distributed index lens of the present embodiment, the positioningof an upper film and a lower film at the time of the process isnecessary as many times as the number of the stages. Thus, as shown inFIG. 29 (a), in the case where the upper film is flush with the lowerfilm in the designing (surrounded by dotted circles), the pattern tapersoff or disappears by even a small amount of positioning misalignment. Onthe other hand, as shown in FIG. 29 (b), in the case where the upperfilm and the lower film, which patterns having a relatively higheraspect ratio, have already been misaligned in the designing, the patterndeviation can be prevented to the minimum level. A wider positioningmargin can be set in proportion to the width of the wavelength of theincident light, and in the case where the margin is not more than λ/4n,a sharp decrease of the light-collecting efficiency is not observed.

Ninth Embodiment

FIG. 30 is a cross-sectional diagram showing a lens placed on thesolid-state imaging device having a shrinking structure. The solid-stateimaging device is shrunk, so that the deflection component of the lenscan be smaller, and the amount of phase modulation can be reduced. As aresult, the designing of the lens can be simplified and the lightcollecting efficiency can be improved.

The distributed index lens with concentric circle structure isexemplified in the aforesaid embodiments 1 to 9. However, it should benoted that the shape of the distributed index lens can be polygon suchas rectangular, hexagon and the like, as long as the lens has theconcentric structure. Furthermore, the distributed index lens with thetwo-stage concentric structure is exemplified in the aforesaidembodiments 1 to 9. However, the present invention is applicable to thedistributed index lens with multiple-stage concentric structure such asa three-stage concentric structure.

Although only some exemplary embodiments of this invention have beendescribed in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention.

INDUSTRIAL APPLICABILITY

The solid-state imaging device of the present invention enables toimprove performances and implement price reductions for imaging sensorrelated products such as digital video camera, digital still camera, anda camera-equipped mobile phone, and is useful for the relatedindustries.

1. A solid-state imaging apparatus, comprising: a plurality of unitpixels, each of the plurality of unit pixels including a microlens,arranged in a two-dimensional array, wherein said microlens includes adistributed index lens having a modulated effective refractive indexdistribution obtained by including a combination of a plurality ofpatterns having a concentric structure, the plurality of patterns beingdivided into line widths which are equal to or shorter than a wavelengthof an incident light, wherein at least one of the plurality of patternsincludes a lower light-transmitting film having the concentric structureand having a first line width and a first film thickness, and an upperlight-transmitting film having the concentric structure configured onsaid lower light-transmitting film having a second line width and asecond film thickness, and wherein said distributed index lens has astructure in which a refractive index material is dense at a center andbecomes sparse gradually toward an outer side in the concentricstructure.
 2. The solid-state imaging apparatus of claim 1, wherein ashape of the refractive index material differs between a center of afirst pattern of the plurality of patterns and an outer side of a secondpattern of the plurality of patterns.
 3. The solid-state imagingapparatus of claim 2, wherein the refractive index material comprisesone of a silica system material and a resin material.
 4. A solid-stateimaging apparatus, comprising: a plurality of unit pixels, each of theplurality of unit pixels including a microlens, arranged in atwo-dimensional array, wherein said microlens includes a distributedindex lens having a modulated effective refractive index distributionobtained by including a combination of a plurality of zone areas havinga concentric structure, the plurality of zone areas being divided intoline widths which are equal to or shorter than a wavelength of anincident light, wherein at least one of the plurality of zone areasincludes a lower light-transmitting film having the concentric structureand having a first line width and a first film thickness, and an upperlight-transmitting film having the concentric structure configured onsaid lower transmitting film and having a second line width and a secondfilm thickness, and wherein said distributed index lens has a structurein which an effective refractive index of the plurality of zone areas isgreater at a center of the concentric structure and lesser toward anouter side of the concentric structure.
 5. The solid-state imagingapparatus of claim 4, wherein the effective refractive index isdetermined by a volume ratio between a high refractive index materialand a low refractive index material in a zone area.
 6. The solid-stateimaging apparatus of claim 5, wherein the high refractive index materialis made of one of a silica system material and a resin material, andwherein the low refractive index material comprises air.
 7. Asolid-state imaging device, comprising: a lens having a modulatedeffective refractive index distribution by including a combination of aplurality of zone areas with a plural-stage concentric structure, theplurality of zone areas being divided, in a whole area of said lens,into line widths which are equal to or shorter than a wavelength of anincident light, and wherein at least one of the plurality of zone areasincludes a lower light-transmitting film with a first plural-stageconcentric structure and having a first line width and a first filmthickness, and an upper light-transmitting film with a secondplural-stage concentric structure, configured on said lowerlight-transmitting film, and having a second line width and a secondfilm thickness.
 8. The solid-state imaging device of claim 7, wherein avolume ratio between said lower light-transmitting film and said upperlight-transmitting film in a zone area and a volume ratio between saidlower light-transmitting film and said upper light-transmitting film inanother zone area adjacent to the zone area are mutually different. 9.The solid-state imaging device of claim 7, wherein respective linewidths in said lens are defined as approximately λ/2n, where λ denotes awavelength of an incident light and n denotes a refractive index. 10.The solid-state imaging device of claim 7, wherein every line width ofthe plurality of zone areas in said lens is an equal line width.
 11. Thesolid-state imaging device of to claim 7, wherein said lens is formed byat least two kinds of light-transmitting materials having differentrefractive indexes.
 12. The solid-state imaging device of claim 7,wherein said lens includes one of SiO₂, Teraethoxy Silane, TiO₂, ZrO₂,Nb₂O₅, Ta₂O₅, Si₃N₄ and Si₂N₃.
 13. The solid-state imaging device ofclaim 7, wherein said lens includes one of benzocyclobutene,polymethymethacrylate, polyamide and polyimide.
 14. The solid-statelight-collecting device of claim 7, wherein a structure of alight-transmitting film in a vertical cross-section including a centerof said lens, which is formed by combining said upper light-transmittingfilm and said lower light-transmitting film, is different depending on awavelength of an incident light.
 15. The solid-state imaging device ofclaim 14, wherein the structure of the light-transmitting film furtherdiffers depending on a focal length setting for a collected light. 16.The solid-state imaging device of claim 14, wherein the structure of thelight-transmitting film further differs depending on an incident angleof the incident light.
 17. The solid-state imaging device of claim 7,wherein said lens includes a light-transmitting film, formed bycombining said upper light-transmitting film and said lowerlight-transmitting film, as an in-layer lens.
 18. The solid-stateimaging device of claim 7, wherein a light-transmitting film, formed bycombining said upper light-transmitting film and said lowerlight-transmitting film, forms a taper structure in a cross-sectionstructure.
 19. A solid-state imaging apparatus, comprising: unit pixelsthat are arranged in a two-dimensional array, each unit pixel includinga lens, wherein said lens has a modulated effective refractive indexdistribution by including a combination of a plurality of zone areaswith a plural-stage concentric structure, the plurality of zone areasbeing divided, in a whole area of said lens, into line widths which areequal to or shorter than a wavelength of an incident light, at least oneof the plurality of zone areas including: a lower light-transmittingfilm with a first plural-stage concentric structure and having a firstline width and a first film thickness, and an upper light-transmittingfilm with a second plural-stage concentric structure, configured on saidlower light-transmitting film, and having a second line width and asecond film thickness.
 20. The solid-state imaging apparatus of claim19, wherein a center of the plural-stage concentric structure of saidlens is offset from a center of the unit pixel.
 21. The solid-stateimaging apparatus of claim 19, further comprising: a plurality oflight-receiving devices, wherein a central axis of each of saidlight-receiving devices is placed to match a central axis of each ofsaid lenses in said unit pixels located in a center of said solid-stateimaging apparatus, and wherein a central axis of each of saidlight-receiving devices and a central axis of each of said lenses areplaced toward the center of said solid-state imaging apparatus in saidunit pixels located near an edge of said solid-state imaging apparatus.